// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_
#define CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_

#include <stddef.h>
#include <stdint.h>

#include <memory>
#include <string>
#include <vector>

#include "base/macros.h"
#include "base/memory/shared_memory.h"
#include "base/memory/singleton.h"
#include "base/process/process.h"
#include "base/strings/string16.h"
#include "build/build_config.h"
#include "content/public/common/child_process_host.h"
#include "ipc/ipc_listener.h"

namespace IPC {
class MessageFilter;
}

namespace content {
class ChildProcessHostDelegate;

// Provides common functionality for hosting a child process and processing IPC
// messages between the host and the child process. Users are responsible
// for the actual launching and terminating of the child processes.
class CONTENT_EXPORT ChildProcessHostImpl : public ChildProcessHost,
                                            public IPC::Listener {
public:
    ~ChildProcessHostImpl() override;

    // Returns a unique ID to identify a child process. On construction, this
    // function will be used to generate the id_, but it is also used to generate
    // IDs for the RenderProcessHost, which doesn't inherit from us, and whose IDs
    // must be unique for all child processes.
    //
    // This function is threadsafe since RenderProcessHost is on the UI thread,
    // but normally this will be used on the IO thread.
    //
    // This will never return ChildProcessHost::kInvalidUniqueID.
    static int GenerateChildProcessUniqueId();

    // Derives a tracing process id from a child process id. Child process ids
    // cannot be used directly in child process for tracing due to security
    // reasons (see: discussion in crrev.com/1173263004). This method is meant to
    // be used when tracing for identifying cross-process shared memory from a
    // process which knows the child process id of its endpoints. The value
    // returned by this method is guaranteed to be equal to the value returned by
    // MemoryDumpManager::GetTracingProcessId() in the corresponding child
    // process.
    //
    // Never returns MemoryDumpManager::kInvalidTracingProcessId.
    // Returns only ChildProcessHost::kBrowserTracingProcessId in single-process
    // mode.
    static uint64_t ChildProcessUniqueIdToTracingProcessId(int child_process_id);

    // ChildProcessHost implementation
    bool Send(IPC::Message* message) override;
    void ForceShutdown() override;
    std::string CreateChannelMojo(const std::string& child_token) override;
    void CreateChannelMojo() override;
    bool IsChannelOpening() override;
    void AddFilter(IPC::MessageFilter* filter) override;
    service_manager::InterfaceProvider* GetRemoteInterfaces() override;

private:
    friend class ChildProcessHost;

    explicit ChildProcessHostImpl(ChildProcessHostDelegate* delegate);

    // IPC::Listener methods:
    bool OnMessageReceived(const IPC::Message& msg) override;
    void OnChannelConnected(int32_t peer_pid) override;
    void OnChannelError() override;
    void OnBadMessageReceived(const IPC::Message& message) override;

    // Message handlers:
    void OnShutdownRequest();

    // Initializes the IPC channel and returns true on success. |channel_| must be
    // non-null.
    bool InitChannel();

    ChildProcessHostDelegate* delegate_;
    base::Process peer_process_;
    bool opening_channel_; // True while we're waiting the channel to be opened.
    std::unique_ptr<IPC::Channel> channel_;
    std::string channel_id_;

    // Holds all the IPC message filters.  Since this object lives on the IO
    // thread, we don't have a IPC::ChannelProxy and so we manage filters
    // manually.
    std::vector<scoped_refptr<IPC::MessageFilter>> filters_;

    DISALLOW_COPY_AND_ASSIGN(ChildProcessHostImpl);
};

} // namespace content

#endif // CONTENT_COMMON_CHILD_PROCESS_HOST_IMPL_H_
